If you are going to keep the #3 butt stock with it's carbine butt plate I would chose a caliber that doesn't recoil much..
Since I like 7mm, I would have JES Reboring bore the barrel to .284 and chambered to one of the following:
708
7X57 (with short throat for 140 grainers)
7-30 Waters

Also .264 bore would be good for low recoil if you only hunted deer and hogs..
.260
6.5X55

I would also reshape that squarish fore arm tip to look like those that are on Martini & Hagen's single shots..

It's a great life if you don't weaken..